1. Field
The present disclosure relates to vertical-type organic light-emitting transistors and a method for fabricating the same, and more particularly, to technology for off-state leakage current reduction and on-off ratio improvement of vertical-type organic light-emitting transistors.
[Description about National Research and Development Support]
This study was supported by the Veteran Researcher Support Project—Leading Research Support Project of Ministry of Science, ICT and Future Planning, Republic of Korea (National Research Foundation of Korea, Project No. 2011-0028422) under the Seoul National University R&DB Foundation.
2. Description of the Related Art
Organic light-emitting transistors have a function of controlling the light emission characteristics of themselves without any additional driving device by combining organic light-emitting diodes with organic field-effect transistors. Theoretically, organic light-emitting transistors may have higher quantum efficiency and numerical aperture than organic light emitting diodes, and are thus gaining attention as a next-generation light-emitting device. Particularly, vertical-type organic light-emitting transistors have advantages in terms of a short channel length and a high current density, and a low driving voltage as well as easy device integration, as compared to general transistors.
However, vertical-type organic light-emitting transistors studied up to now have a problem: Because a source electrode blocks an electric field produced by a gate voltage, controlling electric charges injected from the top of the source electrode through the gate voltage is not easy. As a result, off-state leakage current between source-drain electrodes increases, and current and on-off ratio of a device is reduced. In this circumstance, Korean Patent No. 10-1427776 has used a method of forming a source insulation film on the top of a source electrode to prevent the injection of electric charges from the top of the source electrode in order to reduce off-state leakage current between source-drain electrodes.
However, in vertical-type transistors having a short distance between a source electrode and a drain electrode, the magnitude of an electric field between the source electrode and the drain electrode is very large, and thus, it is still not easy to control electric charges injected from the sides of the source electrode by the gate voltage. Accordingly, to apply vertical-type organic light-emitting transistors as a next-generation light-emitting device, such as, in the field of displays and lighting, first of all, an issue to be solved is to reduce off-state leakage current between source-drain electrodes to thereby improve the current and on-off ratio.